创建linkedlist集合用来充当容器存储连接

读取properties配置文件,

注册驱动

初始化连接

连接数据库

将链接放入集合中

运用动态代理归还连接

package com.gxa;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.linkedList;
import java.util.Properties;
import java.util.logging.Logger;

public class DataPoolSource implements DataSource {
    //创建一个linkedList集合,用来装创建的链接
    private linkedList conns = new linkedList<>();

    private static Properties properties = new Properties();

    //链接数据库:注册驱动,读取db.properties中的数据,链接数据库,将该段代码写在静态块中


    static {
        try {
            //读内容
            InputStream in = DataPoolSource.class.getClassLoader().getResourceAsStream("db.properties");
            properties.load(in);
            //注册驱动
            Class.forName(properties.getProperty("driver"));
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }

    }

    //初始化链接
    public DataPoolSource() {

        for (int i = 0; i < 10; i++) {
            try {
                Connection conn = DriverManager.getConnection(properties.getProperty("url"), properties.getProperty("username"), properties.getProperty("password"));
                //通过动态代理(Proxy)完成连接的创建和归还
                conns.add((Connection) Proxy.newProxyInstance(DataPoolSource.class.getClassLoader(),
                                new Class[]{Connection.class}, new InvocationHandler() {
                                    @Override
                                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                                        if (!method.getName().equals("close")) {
                                            return method.invoke(conn, args);
                                        }
                                        conns.add(conn);
                                        System.out.println("再次添加一个链接" + conns.size());
                                        return null;
                                    }
                                }
                        )
                );

            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }

    //将链接放入集合中


    @Override
    public Connection getConnection() throws SQLException {
        //从集合中取出连接
        Connection connection = conns.removeFirst();
        return connection;
    }

    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        return null;
    }

    @Override
    public  T unwrap(Class iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class iface) throws SQLException {
        return false;
    }

    @Override
    public PrintWriter getLogWriter() throws SQLException {
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {

    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return null;
    }
}

测试代码

package com.gxa;

import org.junit.Test;

import java.sql.Connection;
import java.sql.SQLException;

public class TestDataSource {
    @Test
    public void test1() throws SQLException {
        DataPoolSource dataPoolSource = new DataPoolSource();

        Connection connection = dataPoolSource.getConnection();

        System.out.println(connection);


        connection.close();
    }
}

运用包装设计模式归还连接

创建一个内部类,实现与被增强对象相同的接口

  class MyConnection implements Connection{

        //记住连接对象
        private Connection connection;

        public MyConnection(Connection connection){
            this.connection=connection;
        }

        @Override
        public void close() throws SQLException {
            conns.add(connection);
        }